CVE-2026-98116

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF snd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation with an mmap_count check performed under the PCM stream lock, but the lock is released long before the buffer is actually freed: snd_pcm_sync_stop(), constraint refinement and do_free_pages() all happen in between. snd_pcm_mmap_data(), on the other hand, takes no lock at all: it validates against the old buffer's state and dma_bytes, remaps its pages into the VMA, and only then increments mmap_count. A concurrent mmap() can therefore slip in between the check and the free. remap_pfn_range() installs writable PTEs for the old buffer's pages without taking page references, and the subsequent do_free_pages() returns those pages to the page allocator while the VMA still maps them. This leaves a stale, writable mapping of freed pages: a page-level use-after-free that can be leveraged for local privilege escalation. Make snd_pcm_mmap_data() participate in the buffer-access scheme introduced for hw_params/hw_free: acquire runtime->buffer_accessing before validating and remapping, and release it afterwards. Buffer reallocation already fails with -EBUSY while accessors are active, and the mmap side now fails with -EBUSY while a reallocation is in progress, so the validate/remap sequence and the check/free sequence can no longer interleave. A reproducer that turns this race into a stale writable mapping of the freed DMA buffer pages is available on request.

Severity

HIGH

CVSS score

7.8 (v3.1)

Vulnerability status

Analyzed

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-25 11:17:42.780000

Last modified

2026-10-28 16:10:22.600000

View original CVE JSON

{
  "id": "CVE-2026-98116",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-25T11:17:42.780",
  "lastModified": "2026-10-28T16:10:22.600",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF\n\nsnd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation\nwith an mmap_count check performed under the PCM stream lock, but the\nlock is released long before the buffer is actually freed:\nsnd_pcm_sync_stop(), constraint refinement and do_free_pages() all\nhappen in between.  snd_pcm_mmap_data(), on the other hand, takes no\nlock at all: it validates against the old buffer's state and\ndma_bytes, remaps its pages into the VMA, and only then increments\nmmap_count.\n\nA concurrent mmap() can therefore slip in between the check and the\nfree.  remap_pfn_range() installs writable PTEs for the old buffer's\npages without taking page references, and the subsequent\ndo_free_pages() returns those pages to the page allocator while the\nVMA still maps them.  This leaves a stale, writable mapping of freed\npages: a page-level use-after-free that can be leveraged for local\nprivilege escalation.\n\nMake snd_pcm_mmap_data() participate in the buffer-access scheme\nintroduced for hw_params/hw_free: acquire runtime->buffer_accessing\nbefore validating and remapping, and release it afterwards.  Buffer\nreallocation already fails with -EBUSY while accessors are active,\nand the mmap side now fails with -EBUSY while a reallocation is in\nprogress, so the validate/remap sequence and the check/free sequence\ncan no longer interleave.\n\nA reproducer that turns this race into a stale writable mapping of\nthe freed DMA buffer pages is available on request."
    }
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          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Primary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-416"
        }
      ]
    }
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